This invention is related to the use of license plates on vehicles which are provided with transponders to transmit information about the vehicle. Transponders for tolling purposes are now well-known but are not arranged in the license plate. Rather, some tolling transponders are arranged in a housing which is attached to the vehicle using the same screws which attach the license plate to the transponder and thus are not in the license plate.
Additional and detailed background of the invention is set forth in the patents issued from the parent applications, namely U.S. Pat. No. 6,662,642, as well as U.S. Pat. No. 6,758,089.